E.g., to avoid the $1000/ton missing-carbon tax, use a manufacturing technique that only adds $500/ton to the cost of concrete, but also generates far more atmospheric CO2 in the process.
An unintended consequence might be that yes companies do correctly follow the law and adding carbon to concrete is successful, but also adding carbon to concrete in high enough volumes makes the lifetime of the concrete lesser when exposed to rainwater for long enough, or something like that, resulting in the need to replace the concrete more frequently.
Its the difference between people acting in good faith vs neutral/bad faith with respect to the intent of the law/regulation/etc..
For example, what if it becomes cheap enough to just convert all the CO2 to CO and we dump masses of carbon monoxide into the atmosphere instead? Or if its cheaper to convert CO2 to CO3 which imminently degrades back to CO2 in the atmosphere - would we be confident that the tax law would correctly handle this scenario where the emissions are technically a different substance? Etc..
Yes, loopholes need patching up. The law doesn't need to be perfect, just good enough that complying with the law is simpler and cheaper than looking for loopholes.
If the regulations are not properly written, they could be an incentive to start cutting down trees to turn to charcoal as a carbon filler. Companies are sometimes heartless like that.
And also, we should probably normalize amendments to laws, instead of canonizing them.
-Goodharts law